This invention is directed to a field of facsimile communication and, more particularly, is directed to an improved facsimile communication method, system and apparatus.
Over the past decade facsimile apparatus has become one of the most popular facilities in an office. It is convenient to transmit document information over a general switched telephone network. Such transmission of documents is possible with facsimile apparatus, even if the documents contain graphic information. However, to obtain maximum benefit from facsimile communication it is necessary for many models of facsimile machines, even those made by different manufactures, to be able to communicate with one another.
In an effort to provide uniformity in the operation of different facsimile machines from various manufacturers, the International Telegraph and Telephone Consultative Committee (CCITT) of the International Telecommunication Union (ITU) has provided recommended procedures of operation for facsimile communication. These recommendations are found in the aforementioned Committee's publication "Data Communication Over The Telephone Network", Volume VIII--Fascicle VIII. 1, published in Geneva (1985) (hereinafter "CCITT Standards"). Operation in accordance with the recommendations provided in the CCITT Standards allows mutual facsimile communication, even if the communicating machines are made by different manufacturers. This ability of mutual communication between machines of different manufacturers is one of the main reasons why facsimile communication has become so popular.
Notwithstanding the ability of various models to communicate with one another, it is always desirable to provide compatible facsimile apparatus which can transmit more rapidly with better quality. Accordingly, the recommendations of the CCITT Standards do not prohibit facsimile machines from providing optional functions. Therefore, there are many facsimile machines which provide one or more optional functions with regard to, e.g., the encoding method, resolution, procedure, etc. In accordance with the CCITT standards, compatible facsimile machines can be used for specific communication when each are provided with the same optional functions. Additionally, they can be used for basic facsimile communication with any other apparatus in accordance with the standards of the CCITT Standards.
According to Recommendation T.30 (as referenced in the abovenoted CCITT Standards) a facsimile call should be completed through five phases, i.e., "Call Establishment" (Phase A), "Pre-Message Procedure" (Phase B), "In-Message Procedure and Message Transmission" (Phase C.sub.1 and C.sub.2), "Post-Message Procedure" (Phase D) and "Call Release" (Phase E). In the initial steps of Phase B, two facsimile machines operating in accordance with the CCITT standards determine whether they are both adapted to implement similar optional features. If so, the remaining phases of communication can be completed in accordance with the particular protocol of those optional features. It is noted that while an optional feature may affect a particular protocol of a portion of communication, the remaining portions would be completed in accordance with the recommendations of the CCITT Standards.
In the last steps of Phase B, the two facsimile machines communicate to synchronize their operation and to compensate for particular line impedences, interference, etc. To do this, phasing, training and training check (TCF) signals are transmitted from the transmitter to the receiver. The phasing and training signals are used for the purpose of establishment of synchronization and automatic equalization of the modem within the receiver. In order to perform this modem training, the phasing and training signals must have a predetermined pattern and length. Therefore, the pattern and length of these signals is specified in Recommendation V.27 ter or V.29 as referenced in the above CCITT Standards.
The training check (TCF) signal, used for verification of modem training, also has a specified pattern and length, Recommendation T.30. Particularly, the TCF signal is specified to be a series of logical zeros ("0") lasting for 1.5 seconds with acceptable error range of 10 per cent. However, this signal comprises a major portion of the transmit time required for a document. As an example, the transmit time of the data necessary to transmit every line of a document, e.g., end of line (EOL) signals, message signals, fill time, etc. (referred to herein as total coded data), depends on the contents of the document to be transmitted, as will be described below. Let us assume that a document can be transmitted within 25 seconds. Comparing this time of 25 seconds to the 1.5 second transmit time of the training check signal, it is obvious that the overall transmit time of a facsimile machine can be decreased markedly if the time to transmit the TCF signal can be reduced or eliminated.